How good is your hearing ? And how do you know ?

Michael, languages are untranslatable. If the language is digital you must not convert it into analog, you must take it as it is. This is for machines not humans, as we are now.
Geoff, yeah, no argument about that.

Is there a different between what I'll call sensitive hearing, and the physiological ability to hear the whole spectrum appropriate to one's age?

Play any instrument or hear anyone's voice, there are so many nuances, some of which are probably perceived beyond our awareness, at least in the beginning. Perception and its processing are very complex and not fully understood things. To a degree it is individual, subjective, but the foundation is common.
"Sensitive hearing" is a talent, an art form.